Path: csiph.com!x330-a1.tempe.blueboxinc.net!feeder1.hal-mli.net!border3.nntp.dca.giganews.com!Xl.tags.giganews.com!border1.nntp.dca.giganews.com!nntp.giganews.com!local2.nntp.dca.giganews.com!news.giganews.com.POSTED!not-for-mail NNTP-Posting-Date: Thu, 19 May 2011 15:21:34 -0500 From: Pete Becker Organization: Roundhouse Consulting, Ltd. Newsgroups: comp.lang.c++ Date: Thu, 19 May 2011 16:21:34 -0400 Message-ID: <2011051916213466006-pete@versatilecodingcom> References: <4dd5764b$0$2413$cc2e38e6@news.uslec.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit Subject: Re: '5'-'0' = 5 alway? guaranteed? User-Agent: Unison/2.1.4 Lines: 34 X-Usenet-Provider: http://www.giganews.com X-Trace: sv3-lM0g2izT1zkIOCl7RRoFeIqLukBWK0//hpEfu9yBVXXPvpQqMFP5tLm13pwsSsKB64wF174UsaFrTwh!U9rgrvKCGjGHLf8dxbjj59cXopeNRDcdsmAo9bNFxDTMtjUG8zN58qE3/2SoG1Pm83qRiwUA X-Complaints-To: abuse@giganews.com X-DMCA-Notifications: http://www.giganews.com/info/dmca.html X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.40 X-Original-Bytes: 2358 Xref: x330-a1.tempe.blueboxinc.net comp.lang.c++:5185 On 2011-05-19 15:58:29 -0400, Noah Roberts said: > On 5/19/2011 12:35 PM, crea wrote: >> "Alf P. Steinbach /Usenet" wrote in >> message news:ir3qlq$a84$1@dont-email.me... >>> * crea, on 19.05.2011 21:13: >>>> I am just programming this kind of thing, and was wondering I according >>>> to >>>> c++ language it is always guaranteed that >>>> '5'-'0' = 5. Character calculations. Because character should be in order >>>> isnt it? Is it guaranteed that they are in order and the difference is 1? >>> >>> Yes. >>> >>> But that does not hold for letters (which are discontiguous in EBCDIC, >>> which the C++ standard "must" support). >>> >> >> ok, good to know also the letter-thing. >> >> > > He's wrong actually. It's a really good bet, but by no means guaranteed. The character representations of the digits 0-9 are required to be contiguous and in ascending order. And there's no similar requirement for any other characters. -- Pete Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The Standard C++ Library Extensions: a Tutorial and Reference (www.petebecker.com/tr1book)